The present invention relates to Mobile IP network technology. More particularly, the present invention relates to supporting proxy Mobile IP registration for nodes that do not support the Challenge Handshake Authentication Protocol (CHAP).
Mobile IP is a protocol which allows laptop computers or other mobile computer units (referred to as “Mobile Nodes” herein) to roam between various sub-networks at various locations—while maintaining internet and/or WAN connectivity. Without Mobile IP or a related protocol, a Mobile Node would be unable to stay connected while roaming through various sub-networks. This is because the IP address required for any node to communicate over the internet is location specific. Each IP address has a field that specifies the particular sub-network on which the node resides. If a user desires to take a computer which is normally attached to one sub-network and roam with it so that it passes through different sub-networks, it cannot use its home base IP address. As a result, a business person traveling across the country cannot merely roam with his or her computer across geographically disparate network segments or wireless nodes while remaining connected over the internet. This is not an acceptable state-of-affairs in the age of portable computational devices.
To address this problem, the Mobile IP protocol has been developed and implemented. An implementation of Mobile IP is described in RFC 3344 of the Network Working Group, C. Perkins, Ed., “IP Mobility Support for Ipv4,” August 2002. Mobile IP is also described in the text “Mobile IP Unplugged” by J. Solomon, Prentice Hall. Both of these references are incorporated herein by reference in their entireties and for all purposes.
The Mobile IP process in a Mobile IPv4 environment are illustrated in FIG. 1. As shown there, a Mobile IP environment 2 includes the internet (or a WAN) 4 over which a Mobile Node 6 can communicate remotely via mediation by a Home Agent 8 and may also include a Foreign Agent 10. In a Third Generation Partnership Project 2 (3GPP2)/CDMA2000 network, the Foreign Agent is implemented in what is generally referred to as a Packet Data Serving Node (PDSN). In the absence of a Foreign Agent in a Mobile IPv4 environment, or in a Mobile IPv6 environment in which a Foreign Agent is not implemented, the Mobile Node 6 can obtain a topologically correct IP address (i.e., collocated IP address) and register this IP address with the Home Agent. (In a Mobile IPv6 environment, this is accomplished via an Access Router rather than a Foreign Agent.) Typically, the Home Agent and Foreign Agent are routers or other network connection devices performing appropriate Mobile IP functions as implemented by software, hardware, and/or firmware. A particular Mobile Node (e.g., a laptop computer) plugged into its home network segment connects with the internet through its designated Home Agent. When the Mobile Node roams, it communicates via the internet through an available Foreign Agent. Presumably, there are many Foreign Agents available at geographically disparate locations to allow wide spread internet connection via the Mobile IP protocol. Note that it is also possible for the Mobile Node to register directly with its Home Agent.
As shown in FIG. 1, Mobile Node 6 normally resides on (or is “based at”) a network segment 12 which allows its network entities to communicate over the internet 4 through Home Agent 8 (an appropriately configured router denoted R2). Note that Home Agent 8 need not directly connect to the internet. For example, as shown in FIG. 1, it may be connected through another router (a router R1 in this case). Router R1 may, in turn, connect one or more other routers (e.g., a router R3) with the internet.
Now, suppose that Mobile Node 6 is removed from its home base network segment 12 and roams to a remote network segment 14. Network segment 14 may include various other nodes such as a PC 16. The nodes on network segment 14 communicate with the internet through a router which doubles as Foreign Agent 10. Mobile Node 6 may identify Foreign Agent 10 through various solicitations and advertisements which form part of the Mobile IP protocol. When Mobile Node 6 engages with network segment 14, Foreign Agent 10 relays a registration request to Home Agent 8 (as indicated by the dotted line “Registration”). The Home and Foreign Agents may then negotiate the conditions of the Mobile Node's attachment to Foreign Agent 10. For example, the attachment may be limited to a period of time, such as two hours. When the negotiation is successfully completed, Home Agent 8 updates an internal “mobility binding table” which specifies the care-of address (e.g., a collocated care-of address or the Foreign Agent's IP address) in association with the identity of Mobile Node 6. Further, the Foreign Agent 10 updates an internal “visitor table” which specifies the Mobile Node address, Home Agent address, etc. In effect, the Mobile Node's home base IP address (associated with segment 12) has been shifted to the Foreign Agent's IP address (associated with segment 14).
Now, suppose that Mobile Node 6 wishes to send a message to a Correspondent Node 18 from its new location. In Mobile IPv4, a message from the Mobile Node is then packetized and forwarded through Foreign Agent 10 over the internet 4 and to Correspondent Node 18 (as indicated by the dotted line “packet from MN”) according to a standard internet protocol. If Correspondent Node 18 wishes to send a message to Mobile Node—whether in reply to a message from the Mobile Node or for any other reason—it addresses that message to the IP address of Mobile Node 6 on sub-network 12. The packets of that message are then forwarded over the internet 4 and to router R1 and ultimately to Home Agent 8 as indicated by the dotted line (“packet to MN(1)”). From its mobility binding table, Home Agent 8 recognizes that Mobile Node 6 is no longer attached to network segment 12. It then encapsulates the packets from Correspondent Node 18 (which are addressed to Mobile Node 6 on network segment 12) according to a Mobile IP protocol and forwards these encapsulated packets to a “care of” address for Mobile Node 6 as shown by the dotted line (“packet to MN(2)”). The care-of address may be, for example, the IP address of Foreign Agent 10. Foreign Agent 10 then strips the encapsulation and forwards the message to Mobile Node 6 on sub-network 14. The packet forwarding mechanism implemented by the Home and Foreign Agents is often referred to as “tunneling.” In the absence of a Foreign Agent, packets are tunneled directly to the Mobile Node 6 collocated care-of address.
Since a node may not support Mobile IP, a node that changes its location within a network cannot initiate registration with its Home Agent. Proxy mobile IP support (i.e., proxy registration) may therefore be performed by a proxy entity other than the node, such as an Access Point, a Foreign Agent, or a Packet Data Serving Node (PDSN) (e.g., in a CDMA2000 network) on behalf of the node. Typically, multiple Access Points, Foreign Agents or PDSNs can be placed throughout a facility to give users the ability to roam freely throughout an extended area while maintaining uninterrupted access to all network resources. Once a node is registered with a Home Agent, packets may be forwarded by the Home Agent to the PDSN or Foreign Agent.
In order to send a registration request on behalf of the node, the proxy entity needs the node's IP address and Home Agent address (i.e., default gateway) in order to compose a registration request packet. In addition, the proxy entity also ascertain's the node's sub-network network mask (i.e., netmask) in order to ascertain whether Mobile IP proxy services are required. Specifically, when the proxy entity determines from the source address of a data packet and the netmask that the node is located on the subnet identical to the subnet of the proxy entity, no Mobile IP service is required on behalf of the node as shown at block. However, when the proxy entity determines from the source address that the node is not located on the subnet of the proxy entity, proxy Mobile IP service is performed by the proxy entity is performed on behalf of the node.
Thus, the proxy entity acts as a proxy Mobile Node to register a client (i.e., node) with its Home Agent. Specifically, the proxy entity identifies or allocates a Home Agent and sends a registration request to the Home Agent to establish a Mobile IP session on behalf of the client. The client receives packets addressed to its home address throughout the Mobile IP session. In this manner, a node may roam while maintaining connectivity to the network.
There are a number of authentication mechanisms that may be used to authenticate a user. These authentication mechanisms include Password Authentication Protocol (PAP), CHAP, Extensible Authentication Protocol (EAP), and Microsoft Challenge Handshake Authentication Protocol (MS-CHAP). However, the Mobile IP protocol operates under the assumption that a CHAP challenge and response are used to authenticate a Mobile Node. In other words, the registration request is required to include the CHAP challenge and response.
During the Mobile IP registration process, a Mobile Node typically provides a CHAP challenge and response in its Mobile IP registration request. Specifically, the Foreign Agent typically advertises a CHAP challenge in an agent advertisement. When the Mobile Node composes a Mobile IP registration request, it includes a Mobile-Foreign Challenge Extension (MFCE) including the CHAP challenge and a CHAP response as a Mobile Node-AAA key to be shared between the Mobile Node and a AAA server. When the CHAP challenge and response are provided to the AAA server, the AAA server uses this information to authenticate the Mobile Node based upon a shared password associated with the CHAP challenge and response.
In a proxy Mobile IP situation in a network such as a CDMA2000 network, the PDSN does not receive a registration request from the node and therefore does not receive a CHAP challenge and response from the node. However, if the node negotiates a Point to Point Protocol (PPP) session using the CHAP protocol, the CHAP challenge and response are received by the PDSN from the node during PPP negotiation. In these situations, the PDSN may generate a registration request on behalf of the node using the CHAP challenge and response received during PPP negotiation.
Unfortunately, many nodes do not support the CHAP protocol. For example, PAP is often the only supported protocol, since it is an older protocol. Since the PDSN does not receive a CHAP challenge and response during PPP negotiation for these nodes, the PDSN cannot construct a registration request including a CHAP challenge and response. Accordingly, proxy Mobile IP is unsupported in these systems.
In view of the above, it would be beneficial if proxy Mobile IP could be supported for nodes that do not use CHAP.